BBES was contracted to carry out multi-million pound infrastructure upgrade works at the data centre in Hounslow, while Norland Managed Services Ltd (NMS) were already contracted to provide mechanical and electrical maintenance and had effective control of the site.

Ipswich Crown Court heard Martin Walton, 27, from Cleveland was killed on 16 October 2010 at Morgan Stanley’s Heathrow Data Centre.

The court heard the function of some new power distribution units being installed was to provide two potential power supply sources to the centre’s data storage equipment.

One source was an existing substation on the site and the other was a new substation installed as part of the works.

The existing power supply was under the control of Norland Managed Services Ltd while the new supply was under the control of Balfour Beatty Engineering Services Ltd.

Connection of the first three of these units to the existing data centre infrastructure was scheduled to take place over the weekend of 16th to 18th October 2010.

Last minute modifications to the units required them to be tested with two live supplies to ensure they functioned correctly before being connected to the data centre’s existing infrastructure.

The first unit was successfully modified, tested and connected to the existing infrastructure.

But Walton, a cable jointer employed by subcontracted company, Integrated Cable Services Ltd, was electrocuted when his forehead made contact with the 415V live terminals of the second unit.

During the sentencing hearing and the earlier trial, HSE told the court the underlying cause of the incident was a succession of failures indicative of the complete breakdown of BBES’s management of health and safety in relation to this project, particularly the breakdown of communication.

While NMS had no role in the construction project, the relevant aspect of their undertaking was the management of the impact of the construction project on the existing operational infrastructure under their control.

NMS issued a permit-to-work to Walton allowing him to reroute the existing site power supply through the new distribution unit, in the knowledge it had the potential to receive a supply from a source not under their control and without confirming that that other supply was isolated.

Balfour Beatty Engineering Services admitted safety breaches and was fined £280,000 in total with £42,240 costs.

Norland Managed Services Ltd of Southwark Street, London was found guilty of a safety breach after an earlier trial and was fined £100,000 with £106,670 costs.

Speaking after the sentencing, HSE inspector Loraine Charles said: “Martin Walton’s death, which had a truly devastating effect on his family and friends, was entirely preventable.

“Although BBES claimed to have been under pressure from a difficult and demanding client, they cannot be excused for having lost sight of the need for the effective control of risks arising from the work being carried out under their control at this data centre.

“Permit to work systems were operated poorly or not at all. Not one person involved in the work at the time of the accident had an accurate overall understanding of the work being carried out and, as a consequence, Martin Walton and others were unknowingly working in the vicinity of exposed live electrical terminals.

“NMS, who were operating an effective permit to work system in relation to the equipment under their own control, made no effort to ensure that the work they permitted did not create risk at the point at which it interacted with equipment under BBES control.”